The term jellyfish refers to hundreds of species of primitive marine animals belonging to the class Scyphozoa, phylum Coelenterata. Coelenterata is a phylum name derived from the Greek words meaning “hollow gut.” It refers to important attributes of a group of invertebrate animals, called coelenterates, having a single internal cavity for digestion and excretion. Jellyfish often become abundant in coastal areas, particularly in late summer, and are regarded as a nuisance. Jellyfish sting swimmers, clog nuclear power plants, and fishing boat nets and, at times can cause severe damage to fishing nets owing to their huge volume and weight. In the water they are beautiful, colorful, and diaphanous creatures, yet most people only see them as a washed-up blob on the beach. Jellyfish can be found in both tropical and temperate waters of the world. The environmental factors affecting the occurrence of jellyfish are temperature, oxygen, salinity, and predation. Some species of jellyfish have great commercial potential. For example, the US coastal waters of the Florida Panhandle and all of the northern Gulf of Mexico provide an ideal environment for the seasonal proliferation of Stomolophus meleagris, which is commonly called the cannon-ball jellyfish. This species is found in abundance in certain areas of the world. For instance, it occurs from Southern New England, USA, to Venezuela and the Gulf of Mexico. One swarm observed at Port Arkansas, Tex., USA was estimated to have drifted through the channel at a rate of approximately 2 million per hour. Jellyfish occur world-wide, being caught in the Indian, Northwest Pacific and Western Central Pacific Oceans by Far Eastern countries including Thailand, Indonesia, Malaysia, the Philippines and China. In 1991, for example, the world harvest of jellyfish was 126,419 tons and Japanese buyers pay up to $25.00 per kilogram for large processed Grade “A” Rhopilema esculenta jellyfish.
Fresh jellyfish contain approximately 95 to 98% water by weight, depending on the particular species and approximately 2 to 3% salt by weight, which is in approximate osmotic equilibrium with salt water. The contents of solids other than salt is extremely low; not much higher than 1% by weight. Protein content is approximately 1.3%. The lipid content of jellyfish is very low. On a wet-weight basis, lipid contents in the range 0.0046 to 0.2% have been reported. The nonpolar lipids of lyophilized jellyfish comprised 31.1% of the total lipids and sterols may account for approximately 47.8% of the nonpolar lipids. The cholesterol content of four species of coelenterates was in the range of 72.2 to 88.8% of the sterol content. Calculated from the above values, the cholesterol content on a wet-weight basis would be less than 0.35 mg/100 gm.
Commercially available processed jellyfish contain approximately 5.5% protein, 25% salt and 68% water, however this type of jellyfish would be for consumption and would need to be desalted prior to consumption. As a food-stuff, the protein content of jellyfish in terms of protein level is similar to foods such as pasta and boiled rice.
Jellyfish proteins consist almost entirely of collagen. Analysis of the amino acid composition of mesogloea hydrolysate showed that glycine is the most abundant amino acid, and that hydroxyproline and hydroxylysine, which are characteristic of collagen, are present. Tryptophan is almost totally absent. Thus, mesogloea contain proteins belonging to the collagen group.